1. Field of the Invention
The present invention relates to a technology that enables a transmission entity and a reception entity to detect a retransmission failure and to locally process a corresponding packet when a retransmission with respect to a particular data unit, for example, a Protocol Data Unit (PDU) fails in a Radio Link Control (RLC) layer of a 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE)-Advanced mobile communication system, and thereby enables the transmission entity and the reception entity to continuously transmit and receive additional data without falling into a deadlock state.
2. Description of the Related Art
In the case of a radio interface of a conventional 3rd Generation Partnership Project (3GPP) mobile communication system, a reliable data transmission has been guaranteed using an Automatic Repeat Request (ARQ) retransmission function in a Radio Link Control (RLC) layer. However, as requirements for a system throughput increases, a retransmission in the RLC layer may have some drawbacks in an aspect of efficiency. To transmit data at even higher rates, a Hybrid-ARQ (HARQ) scheme that is a retransmission scheme in a Physical/Medium Access Control (PHY/MAC) layer has been applied.
The HARQ scheme may reduce retransmission overhead by performing a feedback and a retransmission based on a transmission error in a PHY layer. Generally, as a number of HARQ retransmissions increases, a frame transmission error rate may decrease. However, it may not indicate that all the transmission errors may be detected and be recovered by HARQ. Accordingly, an ARQ retransmission function of an upper RLC layer is still required to provide a relatively low frame transmission rate.
In an RLC ARQ retransmission scheme, a data transmission apparatus may transmit a data unit to a data reception apparatus. When the data reception apparatus fails in receiving the data unit, the data reception apparatus may transmit, to the data transmission apparatus, a transmission failure message, that is, a Not Acknowledge (NACK) with respect to the data unit.
The data transmission apparatus may retransmit the data unit for which the transmission failure message is reported, and thereby recover from a transmission error. However, when a retransmission with respect to the data unit continuously fails and thereby a number of retransmissions exceeds a predetermined maximum number of retransmissions, the corresponding data unit may be processed as a retransmission failure and thereby may no longer be retransmitted.
The data reception apparatus may be unaware of whether the retransmission with respect to the data unit fails and thus, may continuously wait to receive the corresponding data unit and repeat an operation of transferring the transmission failure message to a reception side. In the above continuously waiting state, when the data transmission apparatus continuously transmits additional data, a transmission window of the data transmission apparatus and a reception window of the data reception apparatus may become full. Accordingly, the data transmission apparatus and the data reception apparatus may fall into a deadlock state where it is impossible to transmit or receive the additional data.
In a conventional art, when the deadlock state occurs due to the retransmission failure, the RLC layer may need to transmit an error notice to the upper layer, and operate according to an instruction from the upper layer. Specifically, the upper layer may perform an operation of resetting or releasing a corresponding RLC entity in response to the error notice received from the RLC layer. However, resetting or releasing of the RLC layer as above may use a large amount of time, or may discard all the data currently being transmitted and received, which may result in deteriorating a service quality. Accordingly, there is a desire for a method that may more effectively process an RLC retransmission failure.